1. Field of the Invention
The present invention relates to a capacitor used for a semiconductor device, such as DRAM or SRAM, and more particularly relates to a hollow capacitor and a manufacturing method therefor and further relates a semiconductor device including such capacitor.
2. Background Art
In a semiconductor device utilizing a capacitor, an increase in electrostatic capacitance is usually very important for ensuring the data-retaining characteristics of the semiconductor device. However, as semiconductor devices become progressively miniaturized, the capacitor itself is also miniaturized, thereby resulting in a decrease in the electrostatic capacitance of the capacitor.
DRAM is a representative semiconductor device utilizing such a capacitor. A capacitor having a high electrostatic capacitance has been developed for use in DRAM. A so-called cylindrical capacitor having a cylindrical electrode at one end has been conventionally used as such a capacitor having a high electrostatic capacitance. However, in the cylindrical capacitor, a thick conductive film is formed through deposition, thus increasing an absolute step between a memory cell region and a peripheral region. Such a large absolute step considerably interrupts the shape of a wiring layer and hinders miniaturization of the semiconductor device.
For these reasons, a hollow capacitor has recently been developed as a new capacitor structure. In such a hollow capacitor, one of capacitor electrodes is formed into a hollow configuration, and a dielectric film is provided on the surface of the electrode, and other electrode is disposed to face the one electrode via the dielectric film therebetween.
Such a hollow capacitor employs an oxide film as a dummy pattern to be used in forming one capacitor electrode into a hollow configuration (as disclosed in, e.g., Japanese Patent Application Laid-open Nos. 4-39964 and 9-213906 and U.S. Pat. No. 5,095,346). Isotropic etching is commonly used for removing the oxide film serving as a dummy pattern.
FIG. 11 is a cross-sectional view showing a DRAM memory cell as one example of a semiconductor device utilizing a conventional hollow capacitor.
In the drawing, reference numeral 1 designates a hollow capacitor; 2 a designates a silicon oxide film as an interlayer insulating film, 3 designates a storage node contact; 4 designates a transfer gate; 5 designates a gate electrode of the transfer gate 4; 6 designates a bit line contact; and 7 designates a bit line.
In the conventional hollow capacitor 1, an oxide film is used as a dummy pattern for forming a hollow configuration. When the oxide film is formed through isotropic etching, an oxide film, which is used as an underlying interlayer insulating film for the hollow capacitor formed on the dummy pattern, is inevitably etched away. Accordingly, the interlayer insulating film becomes thinner, thereby resulting in a risk of a short circuit arising between the electrode of the hollow capacitor 1 and the bit line 7.
FIG. 12 is a cross-sectional view showing a high-resistance SRAM memory cell having a storage node and a hollow capacitor formed for the storage node.
In the drawing, reference numeral 11 designates a substrate; 12 designates an access transistor; 13 designates a driver transistor; 15 designates a hollow capacitor; 16 designates load resistor; 17 designates a Vcc wiring pattern; 18 designates a GND line; and 19 designates a bit line.
As a result of presence of the hollow capacitor 15, the electrostatic capacitance of the storage node is increased, thereby improving the resistance of the memory cell to soft-error failures. However, the capacitor 15 is formed on a shared direct contact, so that the complete removal of the oxide film 2b staying at the shared direct contact section within a short period of time is considerably difficult. The oxide film can be completely removed, so long as the time required for removing the film (i.e., a processing time) is extended. However, the processing time cannot be extended for fear that an oxide film serving as an interlayer insulating film may be damaged.
In a conventional hollow capacitor such as that described above, an interlayer insulating film existing below the capacitor is usually an oxide film and may be substantially damaged during removal of the oxide film at the time of formation of a hollow structure. In some cases, there arises a chance of a short circuit arising between the gate electrode and the capacitor. Even if removal of an oxide film does not result in a short circuit, the flatness of the interlayer insulating film will be interrupted. This in turn distorts the shape of a film to be formed on the interlayer insulating film.